For sweeping glass surfaces such as motor vehicle windshields, it is well known to use windshield wiper assemblies which move in oscillating movement in contact with the swept surface of the glass in order to maintain good visibility through the glass, with the windshield wiper assembly having a wiper blade. The wiper blade is generally driven, through an appropriate articulated linkage, by means of a windshield wiper arm which is itself driven by a wiper mechanism to which it is coupled. Most often, the windshield wiper arm is driven in a rotary oscillating movement by means of the output or drive spindle of a drive mechanism which is carried by the body of the vehicle, the drive spindle having a head which is formed with a bore by which it is mounted on the wiper arm, and being coupled to the wiper blade through a shroud.
A cylindrical pivot, generally in the form of a rivet, is usually provided between the head and the shroud. A spring is interposed between the arm or the shroud, on the one hand, and the head on the other hand, so as to apply a predetermined degree of pressure against the swept surface of the windshield during operation.
The cross sectional shape of the shroud is usually in the form of an inverted U, defining side flank portions between which the return spring mentioned above is mounted. This spring is able to work either in compression or in tension, as appropriate for the application to which the windshield wiper is to be put. The wiper blade has an armature which is linked to the flexible wiping strip of the blade that makes the actual contact with the swept surface.
One essential precondition for satisfactory operation of the windscreen wiper is that the applied pressure, i.e. the pressure exerted on the swept surface, should be substantially uniformly distributed over the whole length of the wiping strip. The achievement of this objective is complicated by the fact that windshields of modern vehicles are usually curved. In order to obtain the required distribution of applied pressure on a curved surface, it is known to couple the wiping strip to the armature of the blade through stirrups, yokes, or balancing elements or levers having two branches, which are pivotally mounted on the armature of the blade, and thus, by means of positional adjustment, to provide a substantially uniform pressure distribution.
One example of such an assembly is described and shown in the specification of French published patent application No. FR 2 618 398A, in which a series of small cranks are pivoted on the armature. Unfortunately, though satisfactory as regards pressure distribution, this arrangement is visually unattractive. In addition, it requires a large number of pivot points, and this results in a somewhat high selling price.